The present invention relates to a room temperature-curable organopolysiloxane composition or, more particularly, to a room temperature-curable organopolysiloxane composition having excellent storability before curing and capable of giving a cured silicone rubber having excellent oil resistance not to cause a decrease in the rubbery properties and adhesive bonding to the substrate surface even in contact with engine oils, gear oils and the like so as to be useful as an FIPG sealing material of automobiles.
Conventionally, oil-resistant gaskets, packings and the like shaped from cork, various kinds of organic rubbers, asbestos and the like are widely used for sealing in and around automobile engines. These oil sealing materials are disadvantageous in respect of the troublesomeness in the stock control and process control in addition to the most serious drawback that the reliability of their sealing performance is not always high enough.
Accordingly, it is a trend in recent years that the above mentioned oil-sealing materials are under replacement more and more with FIPG (formed-in-place gasket) type oil sealings by utilizing a room temperature-curable silicone rubber composition which is now high evaluated in respect of the good workability, hermetic sealability and excellent heat resistance.
It is usual that room temperature-curable organopolysiloxane compositions or silicone rubber compositions are compounded with certain inorganic powders such as zinc oxide, zinc carbonate, magnesium oxide, calcium carbonate and the like as an oil-resistance improver when they are to be used as an FIPG material. Basic zinc carbonate or zinc hydroxycarbonate is also known as an oil-resistance improver capable of preventing degradation of the rubbery properties of a cured silicone rubber when it is contacted with an engine oil, gear oil and the like but it is not so widely employed because of the relatively poor storability of the room temperature-curable organopolysiloxane composition compounded therewith.